1. Field of the Invention
The present invention relates to a motor drive apparatus and a motor drive method, and more specifically, relates to a motor drive apparatus and a motor drive method to perform vector control without using a position sensor.
2. Background Art
Recently, as the demand for carbon dioxide emission reduction and the like are growing, more energy-saving feature of, for example, household electrical appliances has been strongly required. Among the household electric appliances, the proportion of air-conditioners, refrigerators and washing machines to the total consumed electrical energy is large. Accordingly, it is important to reduce power consumption of motors mounted on these products.
Under such circumstances, a vector control method without using a position sensor where vector control capable of reducing power consumption is combined with drive control without using a position sensor while estimating a rotation speed and a rotation position of a rotor has been receiving attention. Since the control method does not require a position sensor such as a Hall sensor, miniaturization may be achieved. Accordingly, the method is advantageous in terms of its capability of being adopted to applications where a position sensor is difficult to be attached due to high temperature and high pressure such as the inside of a compressor.
However, conventionally, in the vector control motor without using a position sensor, values loaded at the time of manufacturing have been utilized as motor parameters (i.e., a motor coil resistance, a motor coil inductance and a motor inductive voltage constant). Therefore, it has been unavoidable to be impacted by variations of the motor parameters due to manufacturing variation, temperature, aging deterioration and the like.
By the way, a motor speed and position estimation apparatus to estimate a motor speed and a motor position is disclosed in Japanese Patent Application Laid-open No. 1995-87771. However, the apparatus is not designed for a vector control motor without using a position sensor. Further, a motor inductance cannot be estimated with this apparatus.